TITLE:
A 3-D Shape Model of (704) Interamnia from Its Occultations and Lightcurves
AUTHORS:
Isao Satō, Marc Buie, Paul D. Maley, Hiromi Hamanowa, Akira Tsuchikawa, David W. Dunham
KEYWORDS:
Asteroids; Occultations; Lightcurve
JOURNAL NAME:
International Journal of Astronomy and Astrophysics,
Vol.4 No.1,
March
7,
2014
ABSTRACT:
A 3-D shape model of the sixth largest of the main
belt asteroids, (704) Interamnia, is presented. The model is reproduced from
its two stellar occultation observations and six lightcurves between 1969 and 2011.
The first stellar occultation was the occultation of TYC 234500183 on 1996
December 17 observed from 13 sites in the USA. An elliptical cross section of
(344.6 ± 9.6 km) × (306.2 ± 9.1 km), for position angle P = 73.4 ± 12.5° was fitted. The
lightcurve around the occultation shows that the peak-to-peak amplitude was
0.04 mag. and the occultation phase was just before the minimum. The second
stellar occultation was the occultation of HIP 036189 on 2003 March 23 observed
from 39 sites in Japan and Hawaii. An elliptical cross section of (349.8 ± 0.9
km) × (303.7 ± 1.7 km), for position angle P = 86.0 ± 1.1° was fitted. A companion
of 8.5 mag. of the occulted star was discovered whose separation is 12 ± 2 mas
(milli-arcseconds), P = 148 ± 11°. A combined analysis of
rotational lightcurves and occultation chords can return more information than
can be obtained with either technique alone. From follow-up photometric
observations of the asteroid between 2003 and 2011, its rotation period is
determined to be 8.728967167 ± 0.00000007 hours, which is accurate enough to
fix the rotation phases at other occultation events. The derived north pole is λ2000 = 259 ± 8°, β2000 = -50 ± 5° (retrograde rotation); the
lengths of the three principal axes are 2a = 361.8 ± 2.8 km, 2b = 324.4 ± 5.0 km, 2c = 297.3 ± 3.5 km, and the mean
diameter is D = 326.8 ± 3.0 km. Supposing the mass
of Interamnia as (3.5 ± 0.9) × 10-11 solar masses, the density is then ρ = 3.8 ± 1.0 g·cm-3.